I have the Fumoto drain valve and I would like to take an oil sample without a full drain. My biggest concern is making sure there aren't any contamination on the external part of the valve so that it doesn't distort the results. What is a good way to clean it before taking the sample? Since measurements are done in ppm, I would imagine a little bit of dust or other could make a big difference. My plan is to: 1) Warm up the engine 2) Clean the valve 3) Drain a few ounces then fill the sample bottle. All suggestions appreciated!